\documentclass{beamer}
%\usepackage[orientation=landscape,size=a4,scale=2.7]{beamerposter}
\usepackage[size=custom,height=21.0,width=33.6,scale=2.7]{beamerposter}
\usepackage[utf8]{inputenc}
\usepackage{default}
\usepackage{graphicx}
\usepackage{calc}
\usepackage{tikz}
\usepackage{fontspec}
\usepackage{color}

\usefonttheme{professionalfonts}
\usefonttheme{serif}

%\setmainfont{Gill Sans Pro Cyrillic Medium}
%\setmainfont{P22 Underground CY Pro Demi}
\setmainfont{Open Sans Bold}

\setbeamertemplate{navigation symbols}{}%remove navigation symbols

\makeatletter
\define@key{beamerframe}{c}[true]{% centered
  \beamer@frametopskip=0pt plus 1fill\relax%
  \beamer@framebottomskip=0pt plus 1fill\relax%
  \beamer@frametopskipautobreak=0pt plus .4\paperheight\relax%
  \beamer@framebottomskipautobreak=0pt plus .6\paperheight\relax%
  \def\beamer@initfirstlineunskip{}%
}
\makeatother

\definecolor{slidebg}{HTML}{314046}
\definecolor{slidefg}{HTML}{DEE2EB}

\definecolor{sgreen}{HTML}{8EB000}
\definecolor{sred}{HTML}{CF4500}


\setbeamercolor{background canvas}{bg=slidebg}
\setbeamercolor{normal text}{fg=slidefg}

\newcommand{\slide}[1]{
	\begin{frame}[c]
	\centering
	{#1}
	\end{frame}
}

\newcommand{\pic}[1]{
	\begin{frame}[c]
	\centering
		\begin{tikzpicture}[remember picture,overlay]
		    \node[at=(current page.center)] {
			\includegraphics[width=\textwidth, height=0.8\textheight, keepaspectratio]{{#1}}
		    };
		\end{tikzpicture}

	\end{frame}
}

